This invention relates to a resin molding device and a resin molding method, and particularly to the molding technology for presenting a clear pattern in plastics containing a pigment and also preventing a remarkable lowering of strength.
1. Prior Art
The technology of manufacturing a molding presenting colors and patterns by mixing a pigment in resin has been known for long. Typical of the above is the technology of mixing powder (wood flour) of natural wood in resin to manufacture a molding, the so-called wood plastic, and various technology has been proposed heretofore. Among them, the technology of xe2x80x9ccellulosic granular powder, a wood-like molding and a wood-like productxe2x80x9d disclosed in PCT JP94/00351 (International Laid-Open No.: WO94/20280) will now be described in brief.
The pulverized powder obtained by grinding cellulose material as raw material is ground to obtain granular powder increased in bulk specific gravity, a surface grain which has a diameter smaller than that of the granular powder and is harder than the powder is fixed to the outer peripheral surface of the granular powder to obtain a fixed grain, resin and a pigment are mixed with the fixed grain and molten, and after that, or simultaneously with melting, the mixture is formed into a desired shape by extrusion molding or injection molding. According to this technology, it is possible to provide a method of manufacturing a wood-like product and a wood-like product which has a pattern very close to the grain of natural wood and also has feeling such as the touch or the like close to the natural wood.
The technique about the device for extrusion molding is disclosed in prior art such as U.S. Pat. No. 3,966,857, U.S. Pat. No. 3,388,196 and JP-A-62198435.
2. Disadvantage of the Prior Art
It is, however, true that not only in the above technology, giving of coloring to a resin molding is hard to be incompatible with keeping the strength of the resin molding. That is, it is preferable to incompletely mix resin in order to give coloring to the resin molding, but if done so, the strength of the molding is lowered. On the contrary, if mixing is performed completely, the strength of the molding can be increased, but the coloring fades.
A problem to be solved by the invention is to provide the technology by which giving of coloring to a resin molding is made compatible with preventing a remarkable lowering of strength of the resin molding.
It is an object of the invention to provide a method of manufacturing a molding by which clear colors and patterns can be presented without a remarkable lowering of strength.
It is another object of the invention to provide a mixing device for extrusion molding by which clear colors and patterns can be presented without a remarkable lowering of strength.
Further in detail, listed are the respective objects of the invention.
One object of the invention is to provide a manufacturing method by which clear colors and patterns can be presented without a remarkable lowering of strength and to provide a method of manufacturing a molding having the woody feel.
Another object of the invention is to provide a manufacturing method y which a molding having a clear pattern can be manufactured.
Another object of the invention is to provide a mixing device for extrusion molding by which energy required for manufacture can be held down, and by which a molding having a clear pattern can be manufactured.
Another object of the invention is to provide a mixing device for extrusion molding by which the existing equipment can be utilized to the maximum.
The present invention is intended for accomplishing the described objects.
In one embodiment, the invention is a molding manufacturing method using a mixing device 10 for extrusion molding comprising a main cylinder 11 positioned on this side of a metal mold for shaping a molding and a main screw 12 rotated in the main cylinder 11 for mixing resin material 20 and delivering the same to the metal mold, wherein immediately before delivery to the metal mold, an outer resin material 21 positioned on the inner wall side of the main cylinder 11 is put in the molten state, and an inner resin material 22 positioned on the main screw 12 side is controlled to be from the softening temperature to the melting temperature both inclusive. Moreover, cellulose material is mixed with the outer resin material 21. Furthermore, cellulose material mixed with the outer resin material 21 is fixed grains formed by fixing a surface grain which has a diameter smaller than that of the pulverized powder obtained by pulverizing the cellulose material and is harder than the powder to the outer peripheral surface of the pulverized powder.
The xe2x80x9cmainxe2x80x9dof the xe2x80x9cmain cylinder 11xe2x80x9d means any one of cylinders in multilayer molding, for example, and the only one cylinder in monolayer molding. The xe2x80x9cmain xe2x80x9d of the xe2x80x9cmain screw 12xe2x80x9d means a screw incorporated in the main cylinder, and in the case of using plural screws in the main cylinder, it means all of the screws.
As concrete means for xe2x80x9cimmediately before delivery to the metal mold, putting an outer resin material 21 positioned on the inner wall side or the main cylinder 11 in the molten state, and controlling an inner resin material 22 positioned on the main screw 12 side to be from the softening temperature to the melting temperature both inclusivexe2x80x9d, cited are means for controlling the temperature of a heater for heating the main cylinder and the main screw, means for making the particle size of resin material positioned on the main cylinder inner wall side smaller than that of resin material positioned on the main screw side, and the like.
Here, xe2x80x9cresin materialxe2x80x9d means material used at the time of making a resin molding such as polyvinyl chloride which is thermoplastic resin or the like. Though only the resin as base material will be resin material, if wood flour (cellulose material) is contained in resin, it becomes resin material used in the so-called wood plastic molding.
As for the resin material used in wood plastic molding, it is frequent to use the material obtained by mixing wood flour with resin and pelletizing the same in addition Lo the powdered material obtained by mixing wood flour with powder resin. Further, frequently in order to produce a pattern of the grain of wood, xe2x80x9cresin materialxe2x80x9d is added to wood flour and resin to obtain a mixture of a pigment. In that case, sometimes one kind of a pigment will be sufficient, and sometimes plural kinds of pigments are used. In the case of using plural kinds of pigments, xe2x80x9cresin materialxe2x80x9d can be made by preparing plural kinds of pellets with different pigments and mixing the same.
The cellulose material used in manufacturing fixed grains is ordinarily natural wood, or sawdust, but rice straw and bagasse may be used.
As a method of forming fixed grains by xe2x80x9cfixing surface grains which have a diameter smaller than that of the granular powder and are harder than the powder to the surface of pulverized powderxe2x80x9d, cited are grinding using a ball mill, long-time high-speed mixing using a mixer, and so on. By these methods, fuzz of fibers of the cellulose material is decreased. Processing for removing fuzz of fibers of the cellulose material may be performed separately from fixing of surface grains.
The xe2x80x9csurface grainsxe2x80x9dare metal, metal compounds such as titanium oxide, ferrite, aluminum, nickel, silver, calcium carbonate and the like, and nonmetal such as ceramic or the like.
The percentage of fixed grains mixed with resin to the whole is usually set not more than 30 wt %. The reason is that sometimes the fluidity at the time of melting the material to be molded becomes worse to interfere with molding.
The material formed by mixing fixed grains with resin which is resin material may be pulverulent or be previously molded to be pelletized. In order to bring out a pattern of the grain of wood, sometimes one kind of a pigment will be sufficient, but frequently plural kinds of pigments are used. In order to use plural kinds of pigments, plural kinds of pellets having different pigments in xe2x80x9cmaterial formed by mixing resin and a pigment with fixed grainsxe2x80x9d are prepared and mixed to form xe2x80x9cresin materialxe2x80x9d.
As wood flour in resin material is fixed grains, it is possible to manufacture a wood-like product which has patterns very close to the grain of natural wood on the surface and also has a feeling such as the touch or the like very close to that of natural wood.
Immediately before delivery to the metal mold, outer resin material 21 of the resin material 20 is to be put in the molten state, so that while being clamped between the inner wall of the main cylinder 11 and an inner resin material 22, it is rubbed by the inner wall of the main cylinder 11 to be mixed. Soon at the time of delivery from the forward end of the main screw 12 to the metal mold, the material is clamped between the inner wall of the main cylinder 11 and the forward end part of the main screw 12 to be delivered.
On the other hand, the inner resin material 22 is controlled to be from the softening temperature to the melting temperature both inclusive, so that it is delivered in the state of being little mixed to the metal mold.
Since the outer resin material 21 of the resin material 20 is mixed, the strength will not be lowered remarkably unlike the case in which every resin for forming a molding is mixed merely incompletely.
Moreover, as cellulose material is contained in the outer resin material 21, a molding has the wood feeling brought out on the surface thereof.
Furthermore, since pulverization and fixing of surface grains are performed for cellulose material mixed with resin material, fuzz of the cellulose material can be decreased so as to manufacture a molding heightened in a wood feeling.
In another embodiment, the invention defines a method of manufacturing a molding as described above, wherein the outer resin material 21 is made different from the inner resin material 22 in color.
As means for varying the color of resin material, means for varying the kind of a pigment to be mixed with the resin material is general.
If plural kinds of pigments different in color are mixed with the outer resin material 21 turned to be molten, sometimes it is possible to bring out a delicate tone of color. Mixing to such a degree not to lower the strength of a molding causes the case where as plural kinds of pigments are made monochromatic, sometimes mixing is not completely performed.
According to this embodiment, the outer resin material 21 is not completely mixed with the inner resin material 22 not molten. Accordingly, it is possible to manufacture a molding which will not turn to a color intermediate between the outer resin material 21 and the inner resin material 22.
In another embodiment, the invention defines a method of manufacturing a molding as described above, wherein cellulose material is mixed with the inner resin material 22.
As the cellulose material is contained not only in the outer resin material 21 but in the inner resin material 22, it is possible to provide a molding having a wood feeling all over the molding.
In another embodiment, the invention defines a method of manufacturing a molding as described above, wherein the cellulose material mixed with the inner resin material 22 is formed by fixing surface grains which have a diameter smaller than that of pulverized powder obtained by pulverizing the cellulose material and are harder than that to the outer peripheral surface of the pulverized powder.
In another embodiment, the invention defines a method of manufacturing a molding as described above, wherein the cellulose material mixed with the inner resin material 22 is formed by fixing surf ace grains which have a diameter smaller than that of pulverized powder obtained by pulverizing the cellulose material and are harder than that to the outer peripheral surface of the pulverized powder.
As pulverization and fixing of surface grains are performed for the cellulose material mixed with the inner resin material 22, fuzz of the cellulose material can be decreased so as to provide a molding heightened in a wood feeling of the whole molding.
In another embodiment, a mixing device 10 for extrusion molding comprising a main cylinder 11 positioned on this side of a metal mold for forming a molding, and a main screw 12 rotated in the main cylinder 11 for mixing resin material 20 and delivering the same to the metal mold, immediately before delivery to the metal mold, the outer resin material 21 positioned on the inner wall side of the main cylinder 11 is put in the molten state, and the inner resin material 22 positioned on the main screw 12 side is formed in such a manner as to be controlled from the softening temperature to the melting temperature both inclusive. Moreover, the device includes a sub-throw-in machine for throwing the outer resin material 21 in the mixing device for extrusion molding, and the sub-throw-in machine is provided separately from the main throw-in machine (e.g. main hopper 13) for throwing in the inner resin material 22 and comprises an outer resin material holding part (e.g. sub-hopper 14) for holding the outer resin material 21 and a sub-throw-in hole for delivering the outer resin material 21 to the main cylinder 11, the sub-throw-in hole being communicated with a receiving hole positioned between the metal mold in the main cylinder 11 and the main throw-in machine 13. Furthermore, the receiving hole of the main cylinder 11 (e.g. formed by removing a receiving hole forming member 11A) is formed in such a manner as to expand the receiving hole 11A on the rotating direction side of the main screw 12 in the cylinder inner wall.
The xe2x80x9cmain throw-in machinexe2x80x9d is generally called xe2x80x9chopperxe2x80x9d.
The sub-cylinder of the xe2x80x9csub-throw-in machinexe2x80x9dmay be a hopper, but as defined in the claim 13, it may be provided with a screw.
The receiving hole 11A is expanded by providing a notch part 11F by chamfering using an inversed spot facing tool.
Since the outer resin material 21 of the resin material 20 is put in the molten state immediately before delivery to the medal mold, mixing is performed by rubbing of the inner wall of the main cylinder 11. Soon at the time of delivering the material from the forward end of the main screw 12 to the metal mold, the material is clamped between the inner wall of the main cylinder 11 and the forward end part of the main screw 12 to be delivered.
On the other hand, as the inner resin material 22 is controlled to be from the softening temperature to the melting temperature both inclusive, it is delivered in the state of being little mixed to the metal mold.
As the outer resin material 21 of the resin material 20 is mixed, the strength will not be remarkably lowered unlike the case of quite incomplete mixing.
Moreover, as the sub-throw-in machine is provided separately from the main throw-in machine (e.g. main hopper 13) for throwing in the inner resin material 22, it is easy to put the outer resin material 21 in the molten state and control the inner resin material 22 to be from the softening temperature to the melting temperature both inclusive.
Furthermore, as the rotating direction side of the main screw 12 in the receiving hole 11A is expanded, the outer resin material 21 can be smoothly thrown in.
In another embodiment, the invention defines a mixing device for manufacturing a molding as claimed in claim 20, 14 and wherein the receiving hole 11A is a vent hole 11B previously provided in the mixing device 10 for extrusion molding.
Here, the xe2x80x9cvent hole 11Bxe2x80x9dis an air vent hole provided for removing gas contained in resin material or generated from resin material. As air is let escape from the vent hole 11B according to the kind of resin material and the property of a molding in some case, if there are provided plural vent holes 11B, one can be used as a feed port for the outer resin material 21 and the other can be used as an air vent hole.
Since the ordinary mixing device for extrusion molding is provided with a vent hole, it can be applied, so that the existing equipment can be utilized.
In another embodiment, the invention defines a mixing device for manufacturing a molding as described above, wherein the sub-throw-in machine 15 is provided with a sub-screw 17 rotated in the sub-cylinder 16 for mixing and delivering the outer resin material 21 held in the sub-cylinder 16.
On this side of a metal mold in the main cylinder 11, the outer resin material 21 to be put in the molten state is molten and mixed and then fed into the main cylinder 11 by the sub-cylinder 16 and the sub-screw 17.
In another embodiment, the invention defines the mixing device for manufacturing a molding as described above, wherein there are provided plural (e.g. five) receiving holes of the main cylinder 11 in the direction of extrusion.
As there are provided plural receiving holes 11 of the main cylinder 11 in the direction of extrusion, it is possible to select and use the receiving holes appropriate for a molding according to various conditions such as desired colors and patterns, the kind of resin and the like. Further, the receiving hole can be used as a vent hole.
In another embodiment, the invention defines the mixing device for manufacturing a molding as described above, wherein the area in the main screw 12 that corresponds to the receiving hole is formed in such a manner that the diameter of the main screw 12 is smaller than that of the other area.
The area in the main screw 12 that corresponds to the receiving hole is formed in such a manner that the diameter of the main screw 12 is smaller than that of the other area, whereby the outer resin material 21 can be smoothly thrown in from the receiving hole.